There are yet others having the same structure, but oviform, with respiratory lamellæ upon the absorbent tubes, Rippenquallen or Beroes.
3183. An Acalephan is a brood-egg, which swims freely about without a shell.
3184. The vessels are quaternary in their distribution, and form a cross, like the involucral vessels of the chick.
3185. In these animals the ova first begin to be detached and agglomerated together in definite situations so as to constitute ovaria. The number here is also four.
They lie usually within four cavities surrounding the stomach, and into these wide apertures situated near to the mouth lead; they are at the same time regarded as respiratory cavities.
In other species vesicles, wherein seminal animalcules are developed, occupy the same situation. Here therefore is recognised for the first time a separated sex.
In the Röhrenquallen or Physaliæ the ovisacs mostly depend externally in the form of bells.
Besides this we find in the Acalephæ all sorts of laminæ, which are probably organs of respiration.
It is not known what is the meaning of the air-sacs and of what the air consists.
Most of the species emit light like globes of fire, just as many Infusoria do also. It is probably a phosphorescence given out by the mucus when passing over into a state of decomposition.